text:
What requirements are there to fly into KDCA?
In the A/FD for KDCA, it says:

NOTE: See Special Notices — District of Columbia Ronald Reagan Washington National Airport.

I know that there are special restrictions for flying into DCA, but where is this "Special Notice" that they are referring to, and how can I get permission to fly into DCA under Part 91?

The "special notices" are a section of the A/FD, but those notices paint a very incomplete picture. Both the FAA and the TSA have requirements regarding DCA. The very basics are that you must get authorization from both the FAA and TSA 24 hours in advance, you must have an armed security officer, and you must depart from a gateway airport.
The details are, well...
FAA Requirements

Regulations require an arrival/departure slot to be reserved via the e-CVRS system during most hours, just like other airports designated as high-density airports.
Flights to DCA must originate from within a 1250 mile perimeter (with limited exceptions).

TSA requirements
The TSA requirements are referred to as the DCA Access Standard Security Program (DASSP). An overview is given on this tsa.gov page (scroll down to "DCA Access Standard Security Program").
Details can be found in the Interim Final Rule... because calling the ruling both interim and final won't confuse anyone. Here is a summarization of that document:
Section A. Aircraft Operator Requirements:

Security Coordinators The aircraft operator (company) must have a designated security coordinator who is the point of contact for the TSA and is responsible for implementing the DASSP requirements. This person must undergo a TSA security threat assessment, and a fingerprint-based criminal history records check (CHRC) by the FBI.

DCA Access Standard Security Program (DASSP) TSA will verify the operator's status with the FAA before sending the DASSP document which contains "sensitive security information" which must be implemented, and the operator must notify TSA when all requirements have been implemented.

Flightcrew Members Each flight crew member (does not include flight attendants) must undergo a fingerprint-based CHRC and an FAA record check. Almost any prior restricted airspace violation is an immediate disqualifier.

Flight Approvals Each flight into or out of DCA requires a tentative slot reservation from the FAA (see FAA reqirement #1 above) before applying for TSA authorization. The TSA application must be submitted at least 24 hours prior to aircraft departure. If TSA approves the application, they will transmit this to the FAA which will issue the final slot reservation, and TSA will notify the operator. The TSA only approves up to 48 applications for a given date. The application must include (once per round-trip):

The name, address, and citizen status of each passenger and crewmember (includes flight attendants).
The registration number of the aircraft.
The flight plan.
and... "any other information required by TSA."

Operating Requirements Each flight must:

be operated under instrument flight rules.
not make any intermediate stops between the designated gateway airport and DCA.
have the aircraft, crew, passengers, and property inspected by TSA prior to departure.
have the cockpit door closed and locked for the duration of the flight (if equipped).
have at least one armed security officer who meets the armed security officer requirements.

Costs TSA charges \$15 for each crew member and passenger to conduct the security threat assessment. Additionally, they charge for the screening services at the airport which are "currently estimated at \$296 per round trip into and out of DCA."

Protection of Sensitive Security Infonnation The specific security details described in the DASSP must only be shared on a need-to-know basis.

Other Security Procedures This paragraph basically says TSA can make you do whatever they want... as if that wasn't obvious by this point in the list.

Compliance TSA can perform any inspection or test it wants to verify the operators compliance with DASSP.

Section B. Fixed Base Operator Requirements
That's right, there are two section B's, one right after the other... in case you weren't already convinced the TSA has strong attention to detail.
This section just says there are FBO requirements for gateway airports. Here is a list of Gateway Airports dated March 21, 2013. The list is always subject to change and seems to have more to do with whether there is an FBO at the airport who wants to put up the DASSP more than anything else.
Section C. Armed Security Officer Requirements
Armed security officers must be an active or retired law enforcement officer, or an individual approved by the TSA. This requires a similar background check as the security coordinator and law enforcement training which TSA finds acceptable. For more information, see the Armed Security Officer (ASO) Program.
Flying under Part 91?
At first glance it doesn't seem like there is any rule explicitly prohibiting Part 91 operations in 49 CFR Part 1544, and §1544.1 Applicability of this part. says:

(a) This part prescribes aviation security rules governing the following:
(1) The operations of aircraft operators holding operating certificates under 14 CFR part 119 for scheduled passenger operations, public charter passenger operations, private charter passenger operations; the operations of aircraft operators holding operating certificates under 14 CFR part 119 operating aircraft with a maximum certificated takeoff weight of 12,500 pounds or more; and other aircraft operators adopting and obtaining approval of an aircraft operator security program.

The general definition of an aircraft operator is not limited to an operator with a Part 119 operating certificate. However, the possibility of using part 91 seems to be ruled out by §1544.101 Adoption and implementation. where it enumerates the scenarios TSA is willing to approve, and there are no Part 91 operations in the list.
There are probably a few reasons why Part 91 is not allowed. Most notably:

TSA has specific aircraft operator requirements which an individual operator is unlikely to be able to comply with, and
There are only 48 slots available per day, and therefore preference is given to commercial operators - the explicitly given explanation for why non-airline flights are permitted at all is to permit "operators, their customers, and affected local businesses to recover from the adverse economic impacts brought on by the events of September 11, 2001."

Other fun quotes:

TSA may, at its discretion, require any flight into or out of DCA under this subpart to comply with additional security measures.

and...

In addition, if TSA or the FAMS requires that the aircraft have one or more Federal Air Marshals (FAMs) on board, the aircraft operator must allow the FAM(s) onboard, at no cost to the Federal Government.

and...

TSA may, at its discretion, cancel any or all flight approvals at any time without prior notice to the aircraft operator. For example, if the threat level in the Washington, D.C., area or in the vicinity of any of the gateway airports is set at ORANGE or RED, TSA is likely to cancel any and all flight approvals into and out of DCA.

So, happy flying everyone!

Wikipedia notes (sourced to a TSA page, but page has been moved)

On October 18, 2005 Ronald Reagan Washington National Airport was reopened to general aviation on a limited basis (48 operations per day) and under restrictions: passenger and crew manifests must be submitted to the Transportation Security Administration 24 hours in advance, and all planes must pass through one of 27 "gateway airports" where re-inspections of aircraft, passengers, and baggage take place. An armed security officer must be on board before departing a gateway airport.

The AOPA has more details, but it does not appear to allow light aircraft, instead restricting flights to only:

• Operators under a partial security program approved by TSA under 49 CFR 1544.101(b), which operate aircraft with a passenger seating configuration of 31 or more but 60 or fewer seats.
• Operators under a Private Charter Standard Security Plan (PCSSP) approved by the TSA under 49 CFR 1544.101(f), which operate aircraft with a passenger seating configuration of 61 or more seats or a maximum certificated takeoff weight of 45,500 kg (101,309 pounds) or more.
• Operators in scheduled or charter service with a Twelve Five Standard Security Plan (TFSSP) approved by TSA under 49 CFR 1544.101(d), which operate aircraft with a maximum certificated takeoff weight of greater than 12,500 pounds.
• Aircraft operated by corporations.

The process overview at the linked AOPA page is fairly detailed, but involves several applications, a background check, passenger lists, and more. In addition, the flight must originate from a gateway airport, not just any airfield.


text:
What can a new commercial pilot do to build flight time?
Most new commercial pilots don't have a lot of flight time, so won't be hired by the airlines or corporate operators.
A lot of operations require an air carrier certificate (even though they are a "commercial" pilot, they can't just start flying people around)!
What can they do to build time while (hopefully) getting paid to fly?

For a commercial pilot (without a CFI rating) you've got some options, but the real golden goose of time building is flight instructing. Most folks I know who are time-building accumulate the minimum amount of time until they have enough to get the CFI rating, then go out and instruct to get to their end goal (time / types).
Without the CFI rating, some things to look in to include:

Banner Tow (if available in your area)
Crop dusting (again, if available in your area)
Glider towing
Skydiving
The FAA has a page on skydiving operations this that's worth a read.
Ferry Piloting (if you don't mind the travel)
Photo work - anything from costal erosion photos to event coverage depending on your location.
News work - Hand in hand with Photo work, but also traffic and the like.
Sightseeing flights
AOPA has a page on this which is worth a read, take care as you almost certainly want to be sure you fall under Part 91 and not Part 135!
Deliveries.
Someone needs a wedding cake moved across the state? You can often do that in a Cessna more efficiently than they can by car, and as a commercial pilot you can even charge for it.
Corporate Flight Jobs
Sightseeing within 25sm of an airport

There are some outfits that will "sell" you SIC in their cargo twins. It's a way to build TT, but it's considered an unscrupulous practice.
Many of these will probably require the very time you're looking to build, or experience in specific types of aircraft, but it can't hurt to investigate.

To add on to voretaq7's answer, it also never hurts to hang out at the airport and meet people. I picked up quite a few extra hours as a newer pilot just by being in the right place at the right time. Even if it's just unloggable, ride-along time, it's still good experience. Plus it keeps you in good standing with the other local pilots.

I think delivering multi-tier wedding cake in a GA aircraft is a lot harder than helping the about-to-get-married couple elope.

@Farhan Just keep thinking "smooth air" :-)

Flying a wedding cake (near the end) http://www.adn.com/article/recap-flying-wild-alaska-tundra-taxis

@rbp Ah, you found my reference!

Another option that you can look at is the Civil Air Patrol.  They mostly do disaster reconnaissance flights, though they have several other aviation odd jobs they do for the government.  It  can be really helpful if you know how to use a DSLR style camera because most of their reconnaissance work is done with that type of camera.

One of the most common ways to build time is to instruct.  You will need to get your CFI Rating.  I know you can also tow banners, and possibly sky divers (Not too sure on this one.)

IMHO, this is one of the potentially negative unintended consequences of the 1500 hour requirement. Not everyone is cut out to be a good instructor. It also creates a conflict of interest in that the instructor needs as many hours as possible and the student is trying to get it done without going broke.

Flight training facilities such as CAE or FlightSafety have right seat programs.  You volunteer your time as the right seater during training events.  A great opportunity to learn a jet aircraft and become very familiar with emergency checklists, as well as, networking with a multitude of flight departments.  After a specified number of training events they will type rate you in that aircraft for no cost.  It may be an unpaid position but the experience and networking potential is priceless.

Some EAA chapters share ownership of homebuilt airplanes and members can build flight time by using these planes.  Flight time is flight time and in many cases it doesn't matter that it's a homebuilt (for example, cross-country flying, navigation practice, tail-wheel practice, seaplane practice, basic aerobatics, etc). Homebuilts also give an opportunity to do some aircraft maintenance & repair. It's all good experience.

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text:
Is a light aircraft still usable after a successful airframe parachute deployment?
Some light aircraft now have airframe parachutes. If a pilot does have to pull the chute on a Cirrus (for example), is the aircraft flyable or at least repairable after landing or is it a write-off? What G forces are involved in the impact?
I realize that there are lots of possible variables here, but let's assume that the parachute deploys correctly and in plenty of time for a stabilized descent; touchdown is in 'ideal' conditions, i.e. on level, unobstructed ground; and impact forces are as described in the Cirrus CAPS guide:

The airplane will assume its touchdown attitude to optimize occupant
  protection. The airplane will descend under the canopy at less than
  1700 fpm and ground impact is expected to be equivalent to dropping
  from a height of 13 feet (about 4 meters). The airframe, seats and
  landing gear are all designed to absorb the impact energy.

For the Cirrus at least, it sounds like that the odds are that the plane will be a loss.  Thus far of 53 CAP deployments, only "9 CAPS Planes that Were Repaired and Flew Again"
Revision A7 of the Cirrus SR22 POH currently states "CAPS deployment is expected to result in damage to the airframe" that updates the earlier language that "The system is intended to saves the lives of the occupants but will most likely destroy the aircraft."
https://www.cirruspilots.org/copa/safety_programs/w/safety_pages/723.cirrus-caps-history.aspx

"Expected to result in damage to the airframe" would seem to be the order of the day for all airframe parachute systems -- the airframe might not be a total loss, but it will pretty much definitely be an insurance case for inspection/repair.

In reading the details, I found it interesting that of the 9 planes that flew again, 2 were later involved in serious accidents again.

Airframe damage is expected.  The gear is part of the structure that would be called the "crush zone" in an automobile - an area that is considered expendable as it absorbs energy from the crash to protect the occupants.  Will the airplane be repairable?  Sure!  How much money do you have? Seriously, it is likely the plane will be totalled by the insurance company... and this is why you have insurance.

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text:
What is the procedure to climb and level off using a Bendix/King KAP140 autopilot?
What's the procedure to use the Bendix/King KAP 140 autopilot in the Cessna piston singles to climb to a certain altitude and then capture it and level off?

Are you asking how to work the autopilot? Or is there anything in particular that makes it different for a cessna single?

The KAP 140 was what I was looking for. I just forgot the model number. I'll edit it in.

Only the KAP140 two-axis autopilot with altitude preselect supports capturing a preselected altitude (which is the one installed in the Cessna 172 before the introduction of the Garmin GFC700)
Preselect the desired altitude using the altitude preselect knob, switch to VS mode, select the desired VS and the AP will switch to altitude hold mode when the preselected altitude is reached.
Taken from the manual.


text:
What does account for a high coffin corner of a plane?
The Coffin corner is the altitude at which a plane's stall speed is close to Mach 1, the speed of sound (but still below, at the critical Mach number). What accounts for a coffin corner at higher altitudes? I'd think of a larger wingspan, but on the other hand larger wings would make the plane heavier.

The best you can do is to make the wing loading low. Wing aspect ratio helps, too, and if you look at existing designs, it will be similar to that of gliders and certainly higher than that of airliners or GA airplanes.
This answer covers the characteristics which make a high altitude possible and, besides wing loading, mentions the factor $\text{Mach}^2 \cdot c_L$. Poor designs only achieve a $\text{Mach}^2 \cdot c_L$ of 0.2 whereas good ones will reach 0.4.

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text:
How does IRS estimate the alignment time?
In modern airliners, e.g. A320, once the IRS is starting the alignment process, there is an ECAM message that indicates the alignment time, e.g. IRS IN ALIGN <7 MIN.
How can the IRS estimate the alignment time? From what I understand, the alignment is usually performed using a Kalman filter, which drives the state of the system to a convergence. Is there something in the algorithm that produces convergence time?

Alignment of an IRS is done by mathematical ‘levelling’ of the accelerometers and  gyrocompassing to determine true north.  As this is a purely mathematical process it’s simple enough to predict how close to a solution you are…..a bit like installing software on your PC where it gives you a progress countdown.

Installing a software is writing a pre-determined amount of data to a disk. So if you know the speed at which you write the data, you know how long it will take. For IRS alignment, you do not know the end state, so you could not know how long it will take to reach the end state

Gyrocompassing  measures topple so given that the RLGs will be sensing the magnitude, which dictates the alignment time, I’m sure that it’s not too difficult to work out how long it will take to finish gyrocompassing and therefore alignment.

"Installing software on your PC". You obviously don't use Windows and its notoriously sketchy estimates of time remaining...

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text:
Inspection panels and meaning of "free" in pre-flight check list
In the flight manual (DA-20) in the wing section it is written: “Aileron including inspection panel - visual inspection”. What does the “including inspection panel” part mean?
Also, during In-Cabin check when it’s written e.g. “Free” in relation to different knobs. What is expected exactly? E.g. I see “Carburetor Heat” - “free, OFF” as I have to check if the relevant knob is just pulling in/out freely and leave it in OFF position. But if it’s written just “Free”?

Seems to me to be 2 different questions here. Just because they're both part of the pre-flight inspection doesn't mean they're related. If you'll take the [tour], you'll see that the Q&A model here requires one question per post, or two very closely related ones. Please [edit] this down to one question, then ask the other in a separate post. Nobody will look down on you for doing so.

"including inspection panel" means that when inspecting the wings you should also access any inspection panels - looking up an online manual for the DA20 describes thusly:

The bottom shell of both wings has holes for access panels below the flap and aileron bellcranks. The bottom shell has a hole for an access panel below the B-bolt. This gives access to the B-bolt for removing the wings.

Which means you should probably open any inspection panels which are accessible without tools (ie, a screwdriver) and check the general condition of any parts inside, such as structural spars, linkages, bolts etc.
Related:

What are these circles below the wing?
What are some common aileron failures?

The term "Free" in a checklist against anything such as a knob or lever means that that lever is not impeded from movement in any way and can travel the full range of expected movement. For example, that there is not a control lock in place, or something in the way of its movement or that any bearing have not seized it in place.
The ones which say "Free, OFF" probably have a reason for doing so, the ones that say just "Free" probably sets them in a latter step to something sensible. eg, "Trimmer: Free" - later on pre-takeoff it will say "Trimmer: Set take-off". Contrast to "Mixture: Free, ICO" - its important that mixture is reset to Idle Cut Off after the check for "free"

Thank you, Jamiec. So if it’s “Free” I can check the knob and put it in OFF position? Because I found interesting that for some knobs it’s said exactly “free, OFF” and for some just “free”. I thought that probably I’m free to select required position but for this stuff there is written specifically “as required”. Also thank you for online manual link.

Updated answer with more detail @Sergey

Just to reiterate, @Sergey, "Free" here means "free to move," that is "unrestricted in any way." Very bad things can happen when controls are restricted.

Inspection panels on the wings are usually fastened with screws, ie. they're not meant to be accessed without tools. That is the case on the aircraft I fly, and inspecting them means checking that all panels are in place and secure, ie. you won't end up flying with a big hole on the bottom of your wing.
The ones meant to be accessed without tools and opened during preflight should be specifically called out and described as such in the POH. Indeed, whilst the maintenance manual on page 47 states:

The DA20-C1 aircraft has a small number of access panels. The panels give access for maintenance. Most panels are GFRP moldings. Self-tapping screws or camlock (quick-release) fasteners hold the panels.

the POH does not mention them other than by "visual inspection". This means you're not supposed to access the panels during the preflight, merely look at them and confirm they're there, intact and secured properly.


text:
Airbus' official language
I would like to know which language Airbus uses when they create the original version of their official documents.
So.. which language do they use? German or French?

The official business language of Airbus is English. All official documents are written in English (and then possibly translated, if required).
This is what Fabrice Brégier (former COO of Airbus) said on the topic in 2014:

“Airbus’s language is English. I’m not going to tell you that when there are two French people in my office we speak in English, but we systematically speak English, emails are in English," Bregier said.

(Airbus chief: ‘I no longer think like a Frenchman’, thelocal.fr)
This is also confirmed by the current Airbus Careers FAQ page:

Do I need to speak a foreign language to work at Airbus?
The business language at Airbus is English. Each job listing in the Job Market includes the specific language requirements for the position. Being able to speak French, Spanish or German is also an asset.

(airbus.com)

English is the universal language of aviation.  Few technical publications are translated into other languages (unless an airline wants to pay for it, which they won't).  Mechanics at airlines must learn enough english to read a maintenance manual, even in places like China.  For this reason tech pubs have used an English style standard called AECMA Simplified English since the late 80s.


text:
1978 C152 Battery Discharge in-flight
For the past few months our flying club has been plagued with a problem. The problem is that when we start the plane, we initially have a good surcharge on the ammeter. Then, either we run-up, takeoff, or in-flight the ammeter all the sudden  displays a 5 amp discharge.
Turning the master switch off and on seems to temporarily fix it, but it comes back in minutes. The alternator, regulator, battery, self-resetting field circuit breaker, and over-voltage sensors have all been replaced within the last few months in attempt to fix the problem. But still this problem persists.
Has anyone had any similar issues or have any guess what could cause this?

Sounds like maybe a loose connection/intermittent short.

Can you prove it is truly discharging the battery during flight? It almost sounds like the ammeter (shunt) is reversed.

Track down the consumer.

Is the time between master on and the 5 A drain appearing constant? If so it might give a clue to what's pulling the current. What kind of avionics do you have? A competent tech (I am not) should be able to solve this...

The generator on the engine can put out lots more than 5 amps, so if a 5 amp discharge load suddenly presents itself and the rest of the charging/battery system is functioning normally then that load will be picked up by the system and no discharge will show on the ammeter.
This means that the charging circuit has stopped operating, and the 5 amp load could just be representing the normal lighting/avionics house load, which then runs the battery down. (Next time the 5 amp load pops up, try pulling the breakers one by one until you find which load branch is producing it.)
Proof that the charging system is faulty can be gotten by putting a voltmeter across the battery terminals. Any time the generator system kicks on, it will show about 14.5-14.8 volts and positive current ("+ charge") on the ammeter and anytime it cycles off the ammeter will show negative current ("- discharge") and somewhere around 11.8 volts.

All good stuff. The system is actually a 28v system.  We believe the problem is RPM dependent seems like the alternator trips when the rpm is >1700 for some reason. Master switch reset seems to temporarily fix it. Also, no high-voltage light.

The last thing to check is wiring.  It sounds like an intermittent short to ground that passes through a high resistance load path of some kind first when it makes contact, such that it acts like you turned a heater element on or something, and doesn't trip the breaker.
The wiring harness needs to be "wrung out", using a Digital Multimeter, first for shorts that appear spontaneously when the wire harnesses are jiggled at various places in the charging circuit.
If that doesn't find anything, the next test is Megger, or Meg-Ohmmeter checks, which puts high voltage/low current through wiring runs disconnected from the services, looking for MegOhm values that point to current leakage through the wiring insulation.
Usually you will put 200 or maybe 400 v though the disconnected wires, via the multimeter (milliamps of current), with resistance below some threshold indicating insulation breakdown.
Megger is a very common troubleshooting procedure on airliners, but may be rarely done on light airplanes, so I don't know if you'll even be able to find Megger specifications for the airplane's wiring harness in its documentation.
On transport airplanes, the normal sequence is throw parts at it, problem still comes back, wring out the wiring looking for direct shorts, then insulation breakdown checks as I described.
A 45 year old airplane is likely to have brittle wiring insulation, especially on the engine side of the firewall where all the heat is.

super-knowledgeable answers here

I have the same problem with a 152 model 1978.   There is a small relay hidden behind the trim console by the firewall.  It is small black box about 2" square.
That is your problem.
The same is with a 172 M model that i had but the tiny relay was in the wiring by the master switch.
good luck


text:
What types of wood can be used for making propellers?
Early propellers were made from wood and they still are on some vintage/classic aircraft and reproductions. What types of wood are typically used to make wooden propellers?

Historically, the following woods were used:

Mahogany
Walnut
Oak

Almost all wooden propellers are reinforced to add strength. Fabric or metal coverings can be added too.

What do you mean by "reinforced"? Do you mean by materials other than wood?

@Sander The URL I referenced mentioned that, the entire section at the bottom. I didn't include that here because it was verbose and not directly relevant to the question.

Metal pieces like the one shown have a dual purpose. In addition to reinforcement, it protects the leading edge of the blade from damage when hitting birds, sand or gravel on runway, etc.

Before reading the comments, I would have guessed ash. As strong as oak but lighter and harder.

Propellers should be made from the same type of wood as wing spars: In both cases the requirements are the same, and the wood should have the highest strength to mass ratio. Both need to be light and strong, especially in tension in the case of propellers. However, using a hardwood will help with their resistance against nicks and scratches, so for the highest loadings, hickory, maple and oak are good candidates. Spars use softwood like pine or nordic spruce (wood from higher latitudes grows more slowly and has better strength) which are less often used for propellers. Historically a wide variety of materials has been used.
Culver Props selects maple for the highest strength and otherwise birch. Mahogany and cherry are selected for the looks.
Equally important is the glueing from laminated planks and shaping. The craftsmen at the worlds first propeller company, Chauvière, were first in the business of making toilet seats. Switching to propellers came naturally. Laminating helps to control the density of the wood planks and makes it easier to cut out imperfections, so laminated propellers are better balanced and will be 25% lighter because less allowance has to be made to account for imperfections.

Best of Aviation.se: "first in the business of making toilet seats. Switching to propellers came naturally"

Is it really that important for toilet seats to be that strong???  My goodness, what are you people doing to them?

Key reason for laminating: wood will bend as it dries / absorbs moisture. By cutting it and re-assembling with directions reversed, you can effectively prevent this. So not only does it make the wood stronger (by criss crossing the main direction of the wood you make the strength isotropic; and you prevent crack propagation because there are no "preferred directions" any more), but you also preserve the shape which is very important for efficiency of the propeller. Edge "reinforcement" is there just for erosion control (dust, gravel, etc).

@Floris all agreed except for the isotropic part, which is not relevant for propellers. You want anisotropic strength and stiffness, i.e. all fibres more or less radial to counter the predominant loading. Which is just why wood with its strong anisotropy is (still) such a good material.

@yankeekilo - the point is that you have control over the degree of anisotropy by changing the orientation (and layering). You may want more strength in one direction than another - and bias the lamination accordingly. At any rate, even a small fraction of cross fibers will reduce the chance of the wood splitting.

@Floris it would be nice to have actual layup/ply plan for an actual propeller to see how much cross-graining(if any) there is. As you pointed out, the lamination alone does help immensely with crack propagation. I only found this: http://www.canardaviation.com/PhillipJohnson/Propeller/building_the_propeller.htm

Wooden propellers can be made of virtually any wood, I know Sensenich makes theirs of birch, and the company featured on this episode of "How It's Made" apparently uses maple.
I would assume that hardwoods (birch, maple, oak, etc.) are favored over something like pine or spruce that would be easily dented in operation if the propeller kicks up rocks on the ground, though I can't find a good reference on that.

I doubt lignum vitae would be a good choice though, makes the nose even heavier than it is already.

@ratchetfreak Pusher prop? :-) It'd be pretty durable that's for sure!

The prop should have brass plating in impact areas, so spruce is no disadvantage. Birch is good for lowly-loaded props, and maple a good choice for props with higher loading.

@PeterKämpf Sensenich apparently uses urethane in place of traditional brass bindings for the same purpose on at least some of their props - the inexorable march of progress I suppose :)

http://www.wood-database.com/

For fans of German language I found a paper on "DIN EN 1995-1-1" (PDF), explaining the properties of certain wood and composites of it.

Birch, maple, oak, mahogany or walnut are good choices.
Wing spar material is usually sitka spruce which is too soft for propellers.
I would not sit on a sitka toilet seat either as the slivers from it are toxic.


text:
What's the reasoning for full-stop landings at night but touch-and-gos during the day for passenger currency?
FAR 61.57 says that you need to have completed three takeoffs and landings to a full stop in order to carry passengers at night. However, you only need three touch-and-gos in order to carry passengers during the day.
Why the difference?
Is there some rationale for this?  Are full-stop landings considered safer during the night?

There are three really convincing arguments I've heard for this - I'm not sure which is "correct" and explains the FAA's logic, but personally I suspect it's a little bit of each.

Argument 1: Night landings are "special".
A night landing is definitely different from a day landing - there's much less of a sight picture in the flare unless your airport is in a really bright area or you have a bright moon (and even then it's "different").
If all you're doing is tapping your wheels on the ground and quickly accelerating back to takeoff speed you're missing a lot of what a landing is - bringing the nose down, decelerating to a safe taxi speed, and leaving the runway under control.
Which conveniently brings us to...

Argument 2: "You gotta learn how to taxi all over again!"
That's something my instructor told me, and I didn't really understand what he meant until I was in the plane. Airports are really dark and it's hard to find your way around the taxiways at night. Personally I think a big part of this requirement is the intent that you taxi off the runway and make your way back to the end to shoot another circuit. The hardest thing about my night training - aside from finding the darn airports was taxiing around without getting lost.
(Of course the regs don't say anything about "Taxi off the runway" - they just say "full stop". You can satisfy the legal requirement with "stop-and-go" landings, but there's a nagging voice in my head that says you're not really "getting current" if that's all you do...)

Argument 3: It slows your procedures down, which makes you safer.
Touch-and-Go landings are kinda dangerous if you think about them - Bring the plane in for a landing (which is already a lot of work). Now as soon as all your wheels are on the ground make a mental judgment as to whether you have enough runway to take off from given your current position & rolling start, if so retract your flaps to an appropriate takeoff setting, cram the throttle back in, and take off again..
When you look at them that way it's a bit odd that we have students do them (and there's more than one CFI around on the internet who says it's a lousy teaching tool).
Adding "Oh yeah, and it's dark out!" to that already difficult and dangerous procedure above is just begging for an accident - especially in a retractable gear aircraft (gear lever, flaps lever, and what happens if you miss in the dark cockpit?).

It is also much more difficult to judge distance at night (i.e. runway remaining) and if you misjudge that, it could create a major problem!

@Lnafziger, your answer has my vote!

@Lnafziger absolutely - the only way I was comfortable doing stop-and-go landings in my training was if I could stop before our runway intersections (so I knew I had a good few thousand feet left). It's REALLY HARD to judge distance over the ground when all you have are the runway lights!

I like this answer, especially argument 2. I do agree that slowing down procedures does make you safer. I'm not really on the same page about touch-and-gos being all that more dangerous at night. Then again I do fly out of class D airport near the city with 4400ft of pavement (minus displaced thresholds but still) so it is pretty well lit and lots of room to play. Anyway I am pretty conservative though I'm the type of pilot that lines up at the VERY beginning of the runway, gets right on the centerline, holds the brakes till like 2k+ rpm checking for green, unless tower wants a no delay.


text:
What must ATC do, following a reported laser sighting by a plane?
Supposing a pilot reports having a laser beam shone on them to ATC, what action should they take?
Is the pilot allowed to take evasive action?
Can other planes request clearance to avoid the area?

Here's what the regulations say ATC should do:

Broadcast on all appropriate frequencies a general caution warning every 5 minutes for 20 minutes following the last report;

Include information on the ATIS broadcast for one hour following the last report;

Report the incident through the Domestic Events Network (DEN), or to their overlying TRACON or ARTCC facility.

As for the pilots, lasers are regarded as an emergency, so you are permitted to take evasive action.
Other aircraft are also permitted to request clearance to avoid the area.

Here are the relevant FAA orders:
FAAO JO 7110.65:

10-2-14. UNAUTHORIZED LASER ILLUMINATION OF AIRCRAFT
a. When a laser event is reported to an air traffic facility, broadcast on all appropriate frequencies a general caution warning every five minutes for 20 minutes following the last report.
PHRASEOLOGY- UNAUTHORIZED LASER ILLUMINATION EVENT, (location), (altitude).
b. Terminal facilities must include reported unauthorized laser illumination events on the ATIS broadcast for one hour following the last report. Include the time, location, altitude, color, and direction of the laser as reported by the pilot.
NOTE- All personnel can expect aircrews to regard lasers as an inflight emergency and may take evasive action to avoid laser illumination. Additionally, other aircraft may request clearance to avoid the area.

FAAO JO 7210.3:

2-1-27. REPORTING UNAUTHORIZED LASER ILLUMINATION OF AIRCRAFT
All FAA Air Traffic Control facilities, Federal Contract Towers and Flight Service Stations shall report unauthorized laser illumination incidents through the Domestic Events Network (DEN), providing the following information:
a. UTC date and time of event.
b. Call Sign, or aircraft registration number.
c. Type of aircraft.
d. Nearest major city.
e. Altitude.
f. Location of event (e.g., latitude/longitude and/or Fixed Radial Distance (FRD)).
g. Brief description of the event.
h. Any other pertinent information.
NOTE- Facilities without direct access to the DEN shall forward the information through the overlying TRACON or ARTCC facility


text:
Is it illegal for Joe Public to listen to ATC in the UK?
I recall that in the UK (unlike in the rest of the world) we have a law forbidding the listening to of air traffic control, dating back a century, to the days of paranoia over spies!
What is this law, exactly? Is it illegal for a member of the public to listen to live ATC in the UK? Are there any exceptions?
It seems like something of a grey area, but some sources claim that listening to a delayed feed (or historical recording) works around this law; is this true?

Not unlike the entire rest of the world though, Germany has similar brain-damaged laws. Might be more around.

In Indiana, it's illegal to bathe in the winter. You're not the only country with strange laws :)

Hmm, reminds me of laws prohibiting suicide.

@Terry: The law prohibiting suicide is quite sane if you believe suicide ought to be not done in the first place. It makes assisting somebody else committing suicide a prosecutable act. On the other hand, banning listening to ATC Guard is not sane as its intended purpose is to be heard by anybody in the area who might have to care.

@Joshua My objection to the apparent UK ATC law and laws against suicide is that both are basically unenforceable in my opinion. That is what it was/is that causes the ATC law to remind me of suicide laws. I wasn't thinking of the sanity, whatever that may mean (perhaps morality?) of either. By the way, I am a supporter of assisted suicide (now legal in Oregon) .

Just guessing, but this sounds like something left over from WWII national security interests, I don't know if it is still on the books but at least as of 20yrs ago when I got several FCC certifications in the the US, it was illegal for a convicted criminal (felon) to own a public radio station. During WWII the US was afraid they might send spy information to Japan or Germany (or later Russia) and the law was never removed after the war!

@jwzumwalt you are correct, it’s a law left over from WWII.

Another bizarre UK law: https://politics.stackexchange.com/questions/18949/in-the-uk-whats-the-rationale-for-having-crown-copyright

Yes, it is illegal.
The UK has some very strange ideas about Radio, which bear no resemblance to the reality of physics and how radio actually works. Foremost among those ideas is the idea that you are only legally allowed to listen to transmissions intended for "general reception":

The services that can be listened to under the definition of general reception are:

licensed broadcasting stations;
amateur and citizens' band radio transmissions; and
weather and navigation transmissions

Radio scanners should not be used to listen to any other radio services, including illegal radio stations (pirates) (by virtue of the fact that they are not licensed radio stations).

Aviation-band transmissions are not on Ofcom's list, so even though they are broadcast entirely "in the clear" and anyone with an appropriately tuned AM receiver could hear them you are legally prohibited from listening to them.

Providing feeds to LiveATC would also appear to be a violation, though it's not clear to me that listening to LiveATC streams would put the listener in violation of the law.
From the same Ofcom site:

… it is illegal to listen to anything other than general reception transmissions unless you are either a licensed user of the frequencies in question or have been specifically authorised to do so by a designated person.

and

… it is also illegal to tell a third party what has been heard in a transmission a person has listened to illegally.

So anyone providing UK aviation band transmissions to LiveATC may be in violation of both of those laws, but I'm not certain what that means for LiveATC listeners (that would be a question to ask Ofcom).

I doubt you'll find UK feed on LiveATC for this exact reason, but I'm also curious to know from a listener's perspective; I have seen one site with feeds, on a short delay.

@DannyBeckett There's a bit of a gray area in Ofcom's pronouncements on that page -- If an authorized person captures the radio traffic they might be allowed to disclose its contents (either verbally, in a transcript, or maybe as a recording). You'd need to find someone better versed in UK law than I to figure out that murky legal area though.

The tens of thousands of people with airband receivers (which are freely sold in the UK...) at UK airshows would be quite surprised to hear they're all breaking the law, as would be the armed military police patrolling the premises. Of course it can very well be argued that ATC and aircraft transmitters ARE licensed (as without a license they would not be allowed to transmit in the UK). The last sentence of the statement is telling, seems to indicate that the restriction is only for pirate stations.

@jwenting Just because the law surprises you (and is RIDICULOUSLY STUPID) doesn't mean it's not the law - We have a law in NYC that says you can't shoot rabbits from an elevated train line. The general position in the UK (and many other commonwealth countries, as I understand it) is that airband transmissions are not "general reception transmissions", which means it's a crime to listen to them unless you're an "authorised person". (The practice is the law is RIDICULOUSLY  STUPID and enforcement is largely nonexistent, but that was the case for jaywalking in NYC for decades…)

Is ATC a "navigational transmission"?

Just to throw a quick one in here: Ofcom is the regulator - there is an exact law this comes under, that would give you the necessary information. I seem to recall it comes under the Wiretapping Act, but I could be wrong.

@DannyBeckett I'm not well versed in UK law, but the page I linked to states that There are two criminal offences, under section 48 of the Wireless Telegraphy Act 2006, relating to unauthorised reception. -- there might be other applicable offenses though if you go looking, I assume your laws are as convoluted as ours :)

That sounds like the one actually.

@voretaq7 true, but apparently even those tasked with enforcing the law then don't understand the law. And in my experience those enforcing laws are often overeager to be heavy handed, rather than letting things slip. Of course it's quite possible that there are exceptions in place to the law during specific events, but I've used my scanner at Heathrow and Gatwick freely within sight of the airport security police and they never bothered me (admittedly this was several years ago).

Hrm -- does the UK ever broadcast voice transmissions over it's VORs? (similar to US HIWAS)

"The UK has some very strange ideas about Radio, which bear no resemblance to the reality of physics and how radio actually works." Why should it have anything to do with physics? It is illegal for somebody to take my bicycle if I leave it unlocked in a public street, even though nothing physically prevents it. It is illegal for somebody to listen to ATC, even though nothing physically prevents it. Now, it's hard to argue that listening to ATC causes anybody any problems at all, whereas stealing bicycles clearly does, and that is why I find the law ridiculous. Nothing to do with physics.

@DavidRicherby To steal a bicycle you need to go out of your way to do something (get on the bike, push the pedals, steer). To listen to airband all you need to do is adjust any AM receiver to the appropriate frequency range - you have to actively limit receivers to prevent picking it up. A kid with a crystal radio kit (legal in the UK as far as I'm aware) could break this law entirely inadvertently just by moving the slider on their coil (unless they paint over the airband range on the coil).

@voretaq7 Why does getting on a bike and riding it count as "going out of your way to do something" but switching on a radio and tuning it doesn't? Especially when your average consumer hi-fi radio can't even be tuned to the relevant frequencies. I completely agree that this law is ridiculous, but I don't think this is a compelling argument for why. (And, by the way, there's exactly zero chance of a prosecution being brought for inadvertently, momentarily listening to the frequencies, though it would be far preferable to not have to rely on "illegal but you'd never get prosecuted for it.")

@DavidRicherby I suppose it was a more relevant distinction back in the tube-radio days: Not sure about UK equipment but in the US those sets frequently tuned everything from shortwave up through VHF. I have a couple of Zenith sets that even have "Aviation" on the dial & work pretty well (they'll pull in transmissions better than my handheld receiver, largely due to the better antenna, though they suck down a lot of power to do the job).

@jwenting is right. The law in this area may be ridiculous, but Ofcom are not to be messed with. They take the QRP approach to law enforcement: they try to make their tiny amount of power go a very long way.

Regarding "unless you are ... a licensed user", what is to stop a licensed user trom setting up a LiveATC feed?

Regarding "which bear no resemblance to the reality of physics and how radio actually works" - most laws are kinda like that. Making stealing illegal bears no resemblance to the reality of physics and how stealing actually works. Making murder illegal bears no resemblance to the reality of physics and how murder actually works. And there's certainly no law of physics requiring your power to go through a meter. If they were laws of physics they wouldn't need to be actual laws.

Yes it is illegal.
UK's OFCOM, the Independent regulator and competition authority
for the UK communications industries write

Q. Isn't this all a bit heavy?
A. No. No-one likes their private or business conversations to be
  listened to. Parliament has passed these laws to protect the privacy
  of radio users

Obviously this appears pretty futile to many people, me included.
Practicality or enforceability of law is not an issue that prevents legislation. There are other laws that are more obviously justifiable but which relate to actions that are equally difficult to prevent.

Link does not go to what you quoted.

@RossPresser: OFCOM reorganised their website, I've changed the link to point to the Internet Archive's copy of that web-page.

Forbidding interception is part of ITU Constitution accepted by members: "take the necessary measures to prohibit [...] the unauthorized interception of radiocommunications not intended for the general use of the public" (art. 17, Secrecy). US forbids interception, but also allows a few interceptions explicitly: "It shall not be unlawful under this chapter [...] to intercept any radio communication which is transmitted [...] by any marine or aeronautical communications system". Other countries just forbid interception, no exceptions.

Strictly speaking it is against the law, the transmission is not intended for public reception (indicated by it falling outside of public broadcast frequencies) and you are not the intended recipient.
However you will find that in practice this is ignored on a personal basis.
i.e. yourself listening nobody has a problem with, if you were to then make what you hear available elsewhere whether via retransmission, recording or transcript I would expect a knock on the door from Ofcom

Basic legislation within the EU, specifies that your are allowed to listen to any type of information available on the electromagnetic spectrum. It is up to the users to protect said information by using encryption if so required.
This is not to say that there is not some very restrictive legislation in place in some countries. They just hate the thought of their citizens getting informations of almost any kind. Ignore the law and take your complaints to the courts in Brussels. The local authorities will hate you for that, but you will probably win the case.

Could you add a source for the first part of your answer? the second part also sounds as based on very little facts but rather on your personal ideas.

It's Article 19 - Universal Declaration of Human Rights :
"Everyone has the right to freedom of opinion and expression; this right includes freedom to hold opinions without interference and to seek, receive and impart information and ideas through any media and regardless of frontiers.". The equivalent ECHR article 10 has direct force of law in the EU and outranks UK law. It's a sad fact that some people want sources for such statements, basic human rights ought to be General Knowledge.

It is true that EU law often trumps UK law.

It's illegal in Germany too, and people have actually been convicted, so I'm guessing they're able to work around that somehow. I think the issue is that you're not the intended recipient, so you're effectively "wiretapping" (without the wire). The article you quote seems to want to avoid people (governments) from blocking signals intended for you or general reception. Such as blocking Twitter when someone posts something bad about the president.

@MSalters: UDHR is not EU law, it is an (old) statement from the UN of the rights that we should all strive to promote. In any event, Article 19 is about having the right to receive information that was intended for you--not to receive all information irrespective of the intended recipient; even if it were, balances often need to be struck between various rights: e.g. the right (under Article 12) to protection from arbitrary interference with privacy and correspondence.  The Charter of Fundamental Rights of the European Union would hold more weight, but the UK opted out.

@MSalters: Thus one might instead look towards the European Convention on Human Rights, the rights under which must not be interfered with by public authorities in the UK (owing to the Human Rights Act 1998).  However, the (similar) right to freedom of expression under that convention is qualified: the right can justifiably be restricted for a whole host of reasons.

I would home that eavesdropping is not considered a human right just because it might be easy, or even trivial, in some contexts.

Contact between ATC and Aircraft is purely for Navigation Transmissions and therefore legal. I've never heard them having a general chat other than the odd Merry Christmas Etc.
In my opinion it's general receive.
If it's not illegal to listen to then it's not illegal to pass info on in whatever form, ie web feed.
I've asked ofcom and if I get a reply will post here.
Dave

In your opinion (and everyone else's) it's general receive. However it is not legal for the general public to listen to. I've seen online that OFCOM back this, but I'd be interested to see if they respond. This has long been the reason that LiveATC.net does not publish UK ATC feeds.

"If it's not illegal to listen to then it's not illegal to pass info on in whatever form, ie web feed." That doesn't follow at all. It's not illegal for me to buy a book (or even read it in the book shop without paying for it) but it is illegal for me to reproduce the contents of that book and distribute them to others.

Sorry I don't see the relevance to buying a copyright book and reproducing it for others to read.

The point I'm making it's only illegal to redistribute information that I have illegally obtained myself. I can understand Broadcast Receptions such as BBC or local radio stations because they hold the copyright to their own material. But who holds the copyright to ATC/Aircraft transmissions. If you can't supply feeds for any kind of general reception then why are the amateur radio websdr sites ok or are they not ok. Anyway I don't expect a response from Ofcom, but you never know.

@DaveEdge The relevance of buying a book and reproducing it for others to read is that it proves that the statement "it's only illegal to redistribute information that I have illegally obtained myself" is incorrect. A book is an example of information that you can obtain legally but which it is still illegal to redistribute.


text:
If skydivers cannot jump on a flight, what should I take care of when landing?
Piloting an aircraft, if skydivers cannot jump on a flight, what should I take care of when landing?
Are there any special recommendations which should be taken into account?

You should descend in a controlled way, taking into account that your descent rate should be ≤ 29 mph (less than 13 m/s), once below 2,500 feet.
If the descent rate is higher than that, then there is a risk of the AAD popping the skydiver's reserve parachute, mid-flight.

If I've done the conversion properly, 13m/s = 2559.1ft/min.

Pilots do not typically have a vertical speed indicator other than feet per minute...

There was actually an incident in Germany in 2009, where the parachute opened and the guy (who never intended to jump, and was only along for the ride) was actually pulled from the plane. The BFU published the report last month. Very scary stuff, have a look at the picture of how he had ripped through the fuselage on his way out (page 7).

That is to say, he didn't actually go through the fuselage, he did, however put a considerable dent in the door frame. Luckily, under the circumstances, it held together and the pilot was able to land.

@inafziger in the US maybe ;)

@DanPichelman http://www.wolframalpha.com/input/?i=13+m%2Fs+in+feet%2Fmin agrees at least within 0.1ft/min

can't the guy reset the AAD to prevent activation?

That would require for some rigs to be taken off, which is less than feasable when in a confined space. Also by the time everyone on a flight has switched off his AAD, the plane would  practically already be down.

Perhaps trivial, but your landing weight will be higher than during a standard run sans skydivers, which will have an impact on stall speed, landing distance etc.


text:
Why can't an airplane stall at zero G?

You may be surprised to find out that an airplane can stall at any attitude if the critical angle of attack is exceeded, but it cannot stall at 0 G.

This quote found in the April 2014 issue of Flying magazine, but it seems counterintuitive to me.
Why can't an airplane stall at 0G?

@george - Either, but in space there wouldn't be an atmosphere anyway.

To get 0g and stall at the same time, you basically need drag and thrust to cancel each other or both equal to 0. The relative angle of wing and engine are installed makes it impossible for drag and thrust to cancel each other at high angle of attack. I guess it's possible on a missile whose wing can rotate above critical AoA?

At 0 G the plane does not need to generate any lift, therefore there is no critical angle past which the airfoil cannot generate the lift required.
In addition, a sustained 0 G maneuver is a parabolic arc, which means that in theory your flight path should keep your angle of attack at zero the entire time (in a theoretical, symmetrical airfoiled aicraft). You can't stall because your AoA is constantly 0 degrees and cannot exceed the critical angle.

The critical angle of attack is the point where the airflow separates, not where the airfoil no longer generates lift. Why you shouldn't be able to have a stalled airfoil in 0G seems wrong to me, it would be very hard to maintain 0G though as you'd effectively be a big speed-brake, not what you want to be (a ballistic arc, as you say, is a lot more effective). The key here is "sustained 0G".

The more general case (not requiring a symmetrical airfoil) is to point out that you can't stall because the wing is at the zero-lift angle-of-attack throughout the 0G maneuver.  At least, to a first approximation, i.e. assuming that the thrust line is exactly parallel to the instantaneous direction of the flight path.

It's probably more accurate to say "you cannot maintain 0 G in a stall". Even a stalled airfoil generates some lift -- the stall just means that the lift coefficient drops below the best the airfoil can do, not that it becomes zero. Since the stalled wing produces lift, and this lift is generally not in a direction where it can be canceled out by thrust, it will pull the aircraft away from the freefall trajectory.
And even that isn't completely true in the theoretical extreme. If we imagine an aircraft with fully variable angle of incidence (never mind the engineering problems in building such a thing), we can imagine rotating the wings up to around 90° angle of attack. Then, by symmetry, they will not produce any lift, yet it will be fully stalled. There will be lots and lots of drag, but sufficiently powerful thrust can offset that and make the net motion of the aircraft follow a zero G / freefall trajectory.

+1, this is actually a good way of interpreting the "wrong" statement.

Well, the practical use of this is that you push 0G and then you can retract flaps/slats/whatever immediately and keep 0G until you've reached best-glide speed. So while "you cannot maintain 0G in a stall" is more accurate, it is also less useful.

Experimental tilt-wing aircraft have been built that can do exactly what you describe.

Look at it backwards.

Why are you at zero G? Because your downward acceleration is equal to
the acceleration due to gravity.
Why are you accelerating downwards so fast? Because you're not creating any lift to counteract gravity.
Why are you not creating any lift? Because you are at zero degrees angle of attack!

And that's why you can't stall at zero G. You're always also at zero degrees angle of attack (you can get pedantic, depending how you measure it) when you're at zero G. And stalling is always caused by high angles of attack. And if that doesn't make 100% sense, you should look more into stalls before you dig too deep into how G loading affects stall speed.
EDIT: Many people here seem to be replacing the world "airplane" in the question with the word "wing". 0g flight involves the entire airplane, not just the wing. Sure, you could take a Cessna, strap highly controllable rocket engines to the top of it and drop it from another airplane. Then, use the rocket engines to counteract drag and give downward acceleration equal to the force of gravity. That would give you a stalled wing and 0g.
But that's not really an airplane anymore, and it doesn't really answer the question.
To stall, the wing must exceed the critical angle of attack. That means it must have an angle of attack above zero. That means lift is being created, which means an upward force is acting upon the airplane. That means you are no longer at 0g.
The point isn't that once an airplane is at 0g it becomes unstallable. The point is you have to leave 0g to stall it.
It's also an example of how airspeed is irrelevant to stalling. (Sounds crazy, since we talk about stalling speed!) Stalling isn't about the speed or amount of air flowing over the wings, it's about the angle, path and flow. A wing on the same airplane can be not stalled at 5mph, or stalled at 100mph. It just depends on the angle.

Consider a biplane, with one wing at high incidence and the other at the opposite, low incidence. Both are stalled, but each cancels out the lift of the other. Voilá, a stalled airplane at 0 g. Easier than using rockets, too.

Critical angle of attack or stall angle of attack is by definition the maximum angle at which the stream over the airfoil is still attached. It is also the angle of maximum lift. Beyond this angle, the stream over the airfoil becomes unattached, leading to a sudden decrease in lift.

Now, I think the article is somehow misleading. I think what they mean by stall is the airplane lift not being able to compensate weight. Since the weight in 0G is 0, then obviously it won't "stall" in this definition.
A harder question is whether the airfoil can stall in 0G according to the actual definition. Well, if the airplane is free falling in a straight line with its wings parallel to the ground, the airfoil is stalling, but in reality it will likely enter spiral dive, the airfoil will produce lift (which produces the centripetal force of the spiral) and won't be 0G anymore. An airplane is so that it will naturally adapt to the relative air stream, so it's hard to maintain 0G. You do this following a ballistic trajectory, on which at the top portion of the trajectory you get a short free fall feeling, where the airfoil is not producing lift (zero angle of attack).
source:
http://en.wikipedia.org/wiki/Low-g_condition
http://en.wikipedia.org/wiki/Angle_of_attack#Critical_angle_of_attack

Aircraft is flying in the air by 1 G force that resist the gravity of earth and keep the aircraft stay airborne. So if we lose this lifting force that is generated by the differential pressure between the upper and lower side of the wings, in this case the weight force, it will overcomes the lift and will pull that weight of aircraft to the downward.
So the zero G means the weight will be a little bit more than of lift, And eventually the zero G will account as weightlessness but it will be moving toward the centre of gravity (the earth). Why? because we are still flying at the atmosphere environments.

I am an enthusiast, not a pilot nor an engineer. I'm sorry, but I don't follow your explanation.

this does not answer the question


text:
With the upgrade of the 737 to the Max model, what major changes are incorporated?
The Boeing 737 was originally designed in the 1960's and flew into the 1980's before a major redesign (the 737-700, -800, and -900 models) was implemented.
Coming up in a few years will be the next major revamp of the line as the 737-Max series (737-7, 737-8, and 737-9).
What major changes have been incorporated in these revisions?

There are of course a lot of tiny changes that Boeing would have done to the aircraft that most of us wouldn't notice, but for brevity I've just included the major changes between the 737NG series and the upcoming 737MAX.

The CFM LEAP-1B engine replaces the current CFM56 engines. Some of the significant improvements in fuel efficiency (15% savings minus drag from larger engine touted by CFM) come from a much higher bypass ratio (from 5.3:1 to approximately 9:1) and materials that can tolerate higher temperatures. Chevrons (saw-toothed tips at the end of the nacelle) have also been included to reduce engine noise on takeoff.
The engine change required changes to the nose landing gear to allow enough clearance from the ground, extending the nose gear by about 8 inches (20cm) and modifying the nose gear bay to allow it to fit into the existing space.
The AT (Advanced Technology) winglets replace the 737NG's blended winglets. The AT winglet incorporates two portions, done to reduce the weight required (compared to a larger blended wingtip) while still reducing block fuel burn by about 1.5%.
Fly-by-wire spoiler system reduces the need for long cabling between the cockpit and the spoiler hydraulic actuators, saving weight, reducing stopping distance by quicker actuation and increasing the accuracy of the controls.
Redesigned tailcone and modifications to elevator to improve aerodynamics, removing the requirement for vortex generators (VGs), which improves predictability and control by making the air turbulent, but as a result increasing drag.

So, there are no cockpit changes? :(

@YgorMontenegro, looks like at least some of the new 737s will feature an updated flight deck.

and don't forget a new cabin design. While it is already available as an option on the NG since 2010 the Sky cabin (based on that of the 787) will become standard on the Max.

The flight deck now has large displays and there is an onboard network system and onboard maintenance function. Additionally, the landing gear lever only has two positions with an override button instead of a trigger. (A pilot should never really touch either type of override. Putting gear lever up on the ground is a bad day.) There is also a new optional tire pressure indication system.

There was a lot of changes with the original 737 and the Max.

First of all the original 737 had a wingspan of 93 feet the 100-500 model had this wingspan

the 737NG has a wingspan of 117.5 feet
and the 737 Max has a wingspan of 118 feet, so it has more lift.

Another change would be the engine, the Boeing 737 100-200 had a Pratt & Whitney JT8D,

the 737 300-500 had a CFM International 56-3 series
and the 737 600-900 had a CFM International CFM56-7 series

and the 737Max has a CFM International LEAP-1B
which is the most efficient engine out of the whole 737 series.

Another major change is the winglet.
The winglet started to being put on the 737NG series and it increases efficiency,and lift

but the 737 Max wing has a split tip winglet which increases efficiency and lift by 1% over the original winglet and also the wing is raked like a Boeing 787 to reduce wing tip vortex.
Another major change is lower fuel costs than the original 737 and lower operation costs.
Another change would be the tail cone which is more efficient.
Second to last major change would be touchscreen screens on the back of the seats which modern airplanes like the 787 and the A350 have.

The last major change is the sky interior.

Pictures can be helpful but this may be a bit too many. I think the stuff about the original 737 isn't relevant here, and the Sky Interior and seatback displays are already available on the NG series. Otherwise the illustration of the changes is good.

Yeah, seatback displays are actually usually put in by the airline (as is all of the seating.) They're not so much related to the plane itself. Delta has had them in several of their 737NGs for years, for instance, while Southwest does not put them in their NGs.

Except for the Sky Interior - don't rely on anything else in the interior matching what is in the promotional pictures because that is dependent on each operator.


text:
How do insects decrease aircraft performance?
Is it true that insects hitting the fuselage could decrease aircraft performance and increase fuel consumption? Insects are small in mass. I think even a large amount of them accumulate on the aircraft's outer skin, it wouldn't be significantly enough to affect fuel consumption.

it's not about weight, it's about being aerodynamic. Dead insect bodies are small bumps that will disturb the airflow.

Insects are very much small compare to jets. How can a small objects effect aerodynamic of the plane?

That's the difference between smooth attached flow and detached turbulent flow.

It's  bugs on the leading edge of the wing and tail plane rather than on the fuselage that cause problems. Years ago I used to give flight instruction in a J-3 floatplane with 85 hp. We were operating in a very buggy environment a good part of the time. At fuel fuel and with a heavy student, it was often necessary to clean the leading edge of the wing before we could lift off. As @ratchetfreak said, it's the difference between smooth attached flow and detached turbulent flow.

We were operating in a very buggy environment a good part of the time. See? Should have turned on the debugger in your environment. Couldn't resist the little IT joke @Terry. :D

@TBBT just a little note - you can get bug wipers for sailplanes.  I've never seen them in operation, but they do exist - a cable-driven pad that runs out along each leading edge.

Related: http://aviation.stackexchange.com/q/829/95

@Andy quite the acccessory for the serious glider pilot in summer/buggy weather. The difference is very much noticeable after a long day with lots of insects.

A butterfly could flap its wings and trigger a tornado.  Extra fuel will be needed to divert around that tornado ;-)

my glider app on my phone has a performance page, and one of the settings is "bugs", meaning how buggy is the leading edge

See https://en.wikipedia.org/wiki/Birgenair_Flight_301 for how insects living in a Pitot tube can adversely affect aircraft performance...

@TBBT: Crystals of frost are also very small compared to jets, yet they can easily bring down a plane.

Think how important, on a car, is the detail of the surface where the tire touches the road.

"How do insects decrease aircraft performance?" -- they hang from the ceiling inside the cabin and flap their wings and pull the plane downwards!

You're right, insects are very small, so they influence things which happen on their scale. The one important phenomenon on an airliner which has the scale of insects is the boundary layer, the sheet of air around all wetted surfaces where air speed changes from zero (relative to the plane) to the speed it has at some distance. This is called the boundary layer. Its thickness changes from zero at the stagnation point to several centimeters at the end of a long fuselage.
What does the boundary layer look like?
At the leading edge, the boundary layer starts with a thickness of zero. Now friction with the wing will cause some air molecules to be slowed down, and soon you get a sheet of air in which the molecules closest to the aircraft's skin will move with the skin, and the more you move away from the skin, the less they are slowed down. Initially, the layers of air within the boundary layer show no cross movement of molecules. Compare it with a multi-lane road with bumper-to-bumper traffic where no car changes lanes. Since all molecules move along their layer of air, this is called laminar flow (lat. lamina = layer).
At some point downstream oscillations will develop, and once they become unstable, molecules will move between the layers of air. Now you have faster ones from more distant layers moving closer to the skin and kicking the slow ones there ahead, and slower ones from close to the skin moving away, slowing down the more distant layers. Now the cars in your multi-lane road cross lanes, and the result is that all lanes but the rightmost one will move at similar speed. Since the cross-flow is the result of turbulence, this boundary layer is called turbulent.

Speed profiles of laminar (left) and turbulent (right) boundary layers. Image source.
Consequences for drag
The cross flow causes the turbulent boundary layer to have a much steeper speed gradient at the aircraft skin, causing much more friction drag. At the same time, more energy is taken from the flow due to friction, so the whole boundary layer becomes thicker. If you look at the local friction drag, the parameter plots made possible by XFOIL are quite illuminating.

Friction drag over chord for an E502mod airfoil at 3° AoA. Blue: Top surface, Red: Bottom surface.
The plot shows the friction over chord for an airfoil at 3° angle of attack. All flow is attached (save for one small separation bubble on the bottom near the transition point). Can you spot the transition points from laminar to turbulent flow? Yes, it's where the friction drag jumps up and stays annoyingly high downstream. Note that the flow around an airliner's wing happens at a much higher Reynolds Number, so the transition points are closer to the leading edge than in the plot above. I chose the low Reynolds Number in the plot above because it shows the phenomenon more clearly.
But you see also a friction spike at the nose! This is caused by the very small thickness of the young boundary layer. Even though it is laminar, it shows a high friction contribution simply because it is still very thin. Now imagine you have both effects, a thin boundary layer and the bigger friction of a turbulent boundary layer, added together. This is what bugs at the leading edge of the wing will give you! They make the wing's surface rough and drive up friction losses due to an early transition of the boundary layer into turbulent flow.
Consequences for maximum lift
But there is also a second effect: The longer the boundary layer develops, the more the flow loses the ability to slow down and increase pressure towards the trailing edge. A flow's energy is either speed or pressure, but if the energy of the flow is sapped by friction, none of both is left when needed to negotiate the last half of the wing's shape. The flow will separate earlier if it had been turbulent from the beginning, and the wing will stall at a lower angle of attack. This is the second negative consequence of bugs on a wing. It can be mitigated by careful airfoil design, but then this airfoil will show lower bug-free performance.
Glider pilots know this very well, especially those who flew planes which used the Wortmann FX 67-170 airfoil. It had excellent L/D without bugs, but both rain and bugs converted the plane to something resembling a brick. I once flew a Janus B into a shower, and minimum speed increased from 80 km/h to 110 km/h. A few seconds of flying at higher speed cleaned the wing, but then it was time to land, because I had lost so much altitude.

Wow, that's incredible. Football might be a game of inches, but flying an aircraft is a game of millimeters!

The issue here is not the additional mass or weight, but the disturbed airflow over the wings. The key terms here are laminar flow and turbulent flow.
The below picture will show normal laminar and turbulent flow over a wing. With insects or other dirt on the leading edge, the transition will happen closer to the front, leading to a decrease in performance.

(Image Source: www.allstar.fiu.edu)
The NASA has done some reasearch too:

Anyone who has driven through a cloud of insects knows how quickly the bug guts build up on the vehicle, causing problems with visibility, clogging the air intake and radiator, and ruining the car's exterior finish.
The problem for an airplane is that its aerodynamic design is meant to have air move very smoothly across the body and wing surfaces, which is called laminar flow. When there is a disruption in that laminar flow, such as from the accumulation of dead bug parts, you induce the opposite of laminar flow, which is turbulence.
[...]
Finding ways to maintain laminar flow through all phases of flight is a big deal for the aviation community because it could save millions in fuel cost, while also reducing the amount of noxious emissions released into the atmosphere.

So, how serious this problem is in typical flights?

Please! Turbulent and laminar is one thing, and attached and detached/separated flow is a different thing altogether. Both laminar and turbulent flow are attached (they separate only at the trailing edge). Flow separates ahead of the trailing edge only close to stall, and mostly after the laminar-turbulent conversion, but not in regular flight.

@TBBT Unless you fly through a dense swarm of insects, the buildup will not be significant enough to cause issues. For GA aircraft, they are mostly cleaned at the end of day. For commercial aircraft, it's sometimes not a bad idea to take them through a small shower. But commercial aircraft are cleaned as well, from time to time.

@PeterKämpf You are right, I edited my answer. Does this sound better now or would you rephrase? Feel free to edit...

Now I am happy with the answer.

This is the reason I have always wondered how come commercial planes are always covered with those "pin heads", as in the picture http://goo.gl/M3hiqS Apparently their engineers don't think these uneven things would worsen the flow too much. Weird.

@Stan Those "pin heads" are rivets. They're what holds the plane together!

@DavidRicherby: Can't they use countersunk rivets? Those wouldn't protrude.

@curious_cat I'm sure they would, if it was important. Perhaps the difference is that you can afford to mess up the aerodynamics a little bit by having regular bumps over some of the body, but you can't afford to have irregular bumps all over it. In particular, I suspect you won't find any rivets on the leading edge of the wing, which is where a lot of insect mess accumulates.


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What are the technologies used in A320 autopilot?
In the newest aircraft, autopilots are of paramount importance, but how are they designed? What is the hardware used to run them (I guess it is quite different from my laptop)? What is the software (language) used and what are its characteristics (regular clock counter, robust, ...)? This question concerns mainly civil aircraft since I guess that it will be hard to get answers for military ones!
EDIT To make this question answerable and less broad, I would like to have answers focusing on turbojet engine aircraft used as civilian carriers (A320 seems a good candidate to me but I am opened to any other airplane fitting the description).

Even ignoring military aircraft, this question is much too broad to be answered successfully.

@SteveV. I am not looking for the details about the coding or the way an autopilot works just which hardware is used (hard drive? mother board?) and the main features of the software (C++, Fortran, Python and why this choice instead of another). I could split this question in two, but it made sense to me to ask them together and this is exactly the kind of questions I hoped to get answers to in this platform.

Perhaps it could be divided into several questions: a) What are the main components of an autopilot system in a piston engine GA airplane? b) How the autopilot in a piston single or twin differ from turboprop/jet aircraft? c) What is the difference between single-, dual- and three-axis autopilots? d) What have been the top three selling autopilot systems in piston GA aircraft in the last 10 years?  e) What is the embedded software used to program the top selling piston GA autopilot system? Is it different than the software used in second-best selling system?

@ludovic - what makes you think that all autopilots use the same hard drive, or the same programming language?

even just considering piston GA the newer agar in autopilots versus say an STEC are pretty wildly different. I think to be answerable this really needs to be broken down into component questions about specific autopilots/implementations....

@All the comments above: Yeap, apparently it seems that this question might too wide, but all your comments are already a beginning of an answer for me because I really dot know a thing about autopilot systems. In order to make that answerable I will specify further which aircraft I am considering. But an answer stating only the common parts of the different autopilots with some example of the most common solutions would have more than satisfied someone like me with no culture in this domain of aircraft design and usage.

I didn't see the edit to your question until I had written the entire answer below.  I hope it is still helpful.  I'm sure that the autopilots in commercial aircraft are more complex, but probably follow the same basic design. (but hopefully have more redundancy :)

Also, a big difference between piston GA (and most jet GA, with the higher-end jets as the notable exception) is auto-throttles, that is the throttle is connected to the autopilot.  This is notably absent in most GA autopilots, so power management is still an important part of your pilot duties while the autopilot is engaged.

@Canuk I was exactly wondering about this part in my comment below your question and this definitely rises a lot of questions!

Most sophisticated autopilot systems used in modern airliners are integral parts of a larger Flight Management System (FMS). FMS systems include multiple independant computers communicating over one or more common data busses which allow for expandability and upgradability. Examples of the various 'customer facing' independent parts for the B-737, each it's own computer, are one or more Control Display Units (CDUs), Mode Control Panel (MCP), and autopilot logic computers. There are also multiple independent and redundant computers for the various air data and navigation position systems that feed into the FMS.
Each computer is optimized for it's specific task so it is very difficult to answer your question. Characteristically, there is just enough computing horsepower to get the job done and nothing more (and occasionally just a bit less...).

Hopefully the following information will prompt a more specific question (or series of questions):
I looked up S-TEC autopilots because they have an STC (supplemental type certificate) for their autopilot system for over 1,600 models of aircraft.

An autopilot is an avionics system designed to serve two primary purposes:

Enhance a pilot’s flight control capabilities
Reduce cockpit workload by putting the airplane in an automatic flight mode

An autopilot consists of three basic components:

Mode selector/programmer (The device that allows the pilot to program the autopilot to achieve the intended flight profile. This may interact with other avionics, such as a GPS unit)
Computer (This receives the information from the programmer or avionics and sends the appropriate signal to the actuators)
Actuators (The servos or motors which physically move the aircraft's control surfaces)

An autopilot system can be either position-based or rate-based.
Position or attitude autopilots typically use the pilot’s attitude indicator as a gyroscope signal source.
Rate-based autopilot systems use rate gyros and/or accelerometers as primary sensors.
There are many features and functions of an autopilot which are outlined in the referenced PDF file below, but to give you an overview:

Wing Stabilizer (Wing Leveler).
Heading Mode.
Course Tracking and Coupling.
Course Deviation Warning.
Dual Mode Intercept.
Roll Steering.
Altitude Hold.
Vertical Speed.
Pre-Selected Altitude Capture.
Glideslope Coupling.
Trim.
Control Wheel Steering.

Fundamentally, autopilots typically perform the following tasks:

Maintaining Assigned Altitude and Heading.
Holding a heading
Tracking a VOR, GPS, LORAN or LOC signal
Intercepting the course

Each one of these aspects of an autopilot could provide several ideas for questions that could help you get a fuller picture of all the technologies involved in autopilots, and perhaps help you limit the scope of your question to something that might not require textbook-length answer :)
Hope this helps in your quest!
S-TEC Autopilot Overview:
http://sharepoint.s-tec.com/Documentation/Shared%20Documents/Autopilot%20Selection/AutoPilotBook.pdf
S-TEC Pilot Operating Handbooks:
http://sharepoint.s-tec.com/Documentation/default.aspx
Garmin also makes a GA autopilot called the GFC 700 which integrates into their Garmin 1000 flight deck.  More info here: http://www8.garmin.com/learningcenter/training/gfc700/

Thanks for trying to answer my un-answerable question ;) It definitely helps and provides a basis for further questions. Just to make sure, an autopilot also acts on the propulsion part because you just mentioned control surfaces or no?

Control surfaces is just a broad way of encompassing things like the ailerons, elevators and rudder. (There are other control surfaces like canards). The propulsion is the engine, and where an autopilot would fit it is on autothrottles where the autopilot moves the throttle which increases or decreases thrust/power of the engine. This is standard in commercial jets and rare (possibly nonexistent) in small piston aircraft.


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Cessna 172/182: Should I set the tank selector to the R.H. tank after parking the airplane?
The single-engine Cessna 172 and 182 aircraft models have a dual gravity-fed fuel system, where you can draw from both the LH and RH tank simultaneously in flight.
I've heard it said that when you are securing the airplane after a flight to leave the tank selector on the RH tank to prevent crossflow if the ramp is uneven. (So you don't end up with all the fuel in one tank).
Is there any merit to this?  Does it actually block the crossflow valve to do this?

Cessna 150 and 152 aircraft don't have a tank selector, just a cutoff valve.

I believe you should follow the manufacturer's recommendation.  What does it say in the POH?

For what it is worth, I have actually seen this happen in a Learjet when it was parked on a slope and the cross-feed was left open.  They came out to the airplane the next day and found the right wing almost touching the ground and the left one high in the sky.

The C172S manual I have says to set the selector to left or right as part of the "securing airplane" checklist:

Fuel Selector Valve -- LEFT or RIGHT to prevent cross feeding

I was also taught to set it to right during my initial training. The idea is to prevent cross-contamination or leaks if one tank is compromised. Another reason is that if you park the aircraft on a slope, you could end up with an imbalance between the tanks, as you said.
So the POH confirms that it prevents cross feeding, at least in that model: you should always check the POH for your specific aircraft.

What would you do if you came out to the airplane and found that one tank had either contamination or a leak? Would you take off on the other tank? Of course not. It doesn't matter what position the fuel selector is in, you'd have to have it evaluated by a competent mechanic before flight.

@rbp Of course you're correct, but by following the POH then only one tank can drain out onto the ground in the case of a leak, or (maybe) need to be emptied and cleaned in case of contamination. Limiting the impact of a problem is the goal, not flying on one tank.

for the once-in-a-million times that it happens, I guess that makes sense.

Yup, it is the once-in-a-million things that make the difference. When everything works correctly, there shouldn't be an issue. It is when that one thing you didn't plan for goes wrong that you are in trouble.

@rbp Parking on a slope happens FAR more often than once in a million....

Then select "off" when parking

@rbp The Cessna 172 (at least) fuel selector doesn't have an off position: it has left, right or both. Hence the question, I guess.

@Pondlife: The C172P planes I used to fly had left/right/both/off.

@FredLarson I guess that makes the point about always reading the POH for the aircraft :-)

@rbp Is there a reason that you would advocate not following the procedures in the POH?  Of course it matters, since there is a specific procedure to follow in the POH. By not following it, you are taking on more liability for coming up with your own procedures if something were to happen.

@Lnafziger as someone explained, the 172 doesn't have "off," so the question is moot. But, in general, I don't see a problem with setting the fuel tank in the off position. I can't imagine an NTSB accident report that says "Pilot failed to turn on the fuel selector, then taxied to the run-up area, performed a run up, then departed with the fuel selector in the off position." The engine wouldn't run for more than 10 seconds before running out of fuel. The only aircraft that would be a problem in is a helicopter, but the helis I fly don't have fuel valves that are accessible from the cockpit.

@rbp well, the question actually asked about putting the fuel selector on the RH position (not off), but my standard answer for questions like this is "follow the manufacturers procedures", and I feel for good reason. I believe that it's a dangerous comment to tell someone that "it doesn't matter" unless you were part of the certification team, and even then, why would there be a procedure if it didn't matter?  At any rate, that's just my opinion and how I look at things....  Maybe food for thought. :)

Fair enough. But when I advocated not following the POH, its because I was under the mistaken impression that there was an OFF position for the fuel selector in the 172. Incidentally, the Cessna 208 POH shutdown procedure has this instruction: "Fuel tank selectors: Both off," so I think the 172 procedure is more about there not being an OFF position at all rather than some philosophical reason about not ever setting it to OFF.

The 1979 Cessna 172 I flew had an "off" selection (pointing backwards)  See this for an example: http://www.free-online-private-pilot-ground-school.com/images/fuel-selector.gif
Maybe new ones don't? The manual for that plane also didn't specify anything about switching the fuel selector after shutdown.

If you leave the tank on dual and you put fuel in the right tank by the time you are ready to put fuel in the left tank some of the fuel will have flowed into the left tank. The right tank would have more pressure from the weight of the fuel than the emptier left tank and as any liquid will do it will try to balance between the tanks. You will end up with less fuel than 2 full tanks. That is why the POH states either right or left tank. It doesn't matter which tank, just that they are not connected when refueling.

This is the first time I've heard this reason. Do you have any idea how much of a difference that would make? It seems like it wouldn't be a material amount, and probably would sort itself out as the fuel can flow both ways (see the diagram here: https://i.sstatic.net/sZOXT.png) so it would just flow back to the other tank if you topped up the other tank.

In my experience with a Citabria (cross-flow fuel tanks without selector valve), this is a very minor effect. If I were trying to fill every last mL of fuel, then obviously this would interfere, but I suspect that the cross-flow is trivial compared to the flow-rate under cruise. The cross-flow tubes just aren't that big.

My aircraft (M20M) fuel selector has left, right, off. My technique (which would apply to any aircraft that doesn't have dual tank feed) is to turn the fuel off when it is parked. I taxi on the lower tank, then switch to the fuller tank to do the runup and take-off on. That assures that both tanks feed fuel, and I'm always departing on the fullest tank.

Cessna 177 has the OFF selection blocked.  Prevents OFF being selected when BOTH was intended. The Fuel selector knob and the plastic cover can be removed to access the OFF position for  maintenance. My POH also to select RIGHT tank when parked or refueling, same as the 172 mentioned earlier.

Is there any merit to this?
Possibly. Think of it like parking on a hill and leaving your car in gear/steering into the kerb, in case the handbrake fails.... it's a precaution, rather than a requirement.
In the case of a Cessna, the fuel tanks in the wings are very long, wide and flat - so it wouldn't take an excessive amount of bank to allow fuel to slowly move from one tank to the other. If that happened to a great enough degree, in theory the fuel could adversely affect handling.
Chances are that the ramp isn't off-level enough to require it, but assuming that it does block the valve (I'd assume it does, as I'm not sure how else it would work) then there's little harm to be done, and some potential benefit in some circumstances.
Does it actually block the crossflow valve?
No idea, I don't own a C172: it seems like a logical conclusion, but I'd check your manual or with the manufacturer.

Just remember to turn it back to dual feed when you set off.


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Are task cards still used in aircraft maintenance?
I used to work for a company making maintenance software for the shipping industry. Each component, from a cylinder in an engine to the furnace has to be inspected after (e.g.) 10,000 running hours, or every 2 years, etc.
My question is:

Are task cards like the one below still used in aviation, or is there a more up-to-date way of working nowadays? (The PDF I got this from is 10,000 pages long)
What must airlines do to ensure their planes are maintained according to schedule?

I voted to close as there are simply too many airlines out there (each with their own maintenance systems), which makes the question too broad. Also, some of the questions asked are rather opinion-based (such as "are paper records still used/usually sufficient" -- each airline comes to their own decision about whether paper records are sufficient).

@Qantas94Heavy RE: each airline comes to their own decision about whether paper records are sufficient, this is the kind of information I'm looking for. Do airlines have a choice over what they use? I thought maybe it was subject to specific regulations?

@DannyBeckett: well so long it was demonstrable to the relevant authorities that using paper records would be manageable, then I suppose it would be fine. The thing is the examples.

@Qantas94Heavy My question, in brief, is: are task cards still used, or is there a more up-to-date system now? I've just been trying to find a PDF online with some Boeing task cards, but I can't find them now. I don't know whether I'm allowed to redistribute the PDF I have, but here's the first page: http://i.imgur.com/Asf99T2.png

@DannyBeckett I feel like this question would be better for now if it just focused on the task card aspect.

I just watched Engineering Giants - Jumbo Jet Strip-Down, following a British Airways 747 on its D-Check in 2012.
At least for BA, it would seem that paper task/job cards are still heavily used. Apparently there are over 12,000 individual jobs.
I've taken a short (7 secs) clip from the episode, showing walls full of task cards:

That is an impressive array of paper!

I'm not sure about for "general maintenance", but the AMT Handbook chapter on inspections has some language that piqued my interest while I was trying to sniff out an answer.
It says that:

The appropriate checklist or checklists must be utilized to ensure that no items will be forgotten or overlooked during the inspection.

The FAA feels so strongly about this they even go on to say:

Always use a checklist when performing an inspection. The checklist may be of your own design, one provided by the manufacturer of the equipment being inspected, or one obtained from some other source.

Task cards are basically a checklist (or I guess more accurately a "check book" - you go through and reference/fill out each card as you perform the task indicated, and the FAA wants mechanics to use checklists (at least on inspections, and with the standard implied OR ELSE hanging out there), so I'd imagine they're still in use in some form (though the paper / PDF product may have been replaced by something fancy and electronic).
I imagine there are some pretty slick electronic checklist/task card systems out there by now (AvPro Software seems to offer one that I stumbled on with a quick Google search, no comments on quality), but I'm just the dumb slob what flies these things and I don't know much about the maintenance end - just enough to know I know enough to be dangerous if left alone with a screwdriver :-)

I know this is an old question but wanted to share my experience with you. The short answer to your first question is: yes, airlines still use task cards in maintenance.
True, information technology has come along in leaps and bounds. Many airlines have leveraged technology in how they produce their task cards, but ultimately, most still rely on paper. The primary reason for this is that each task needs to be signed off by an appropriately licensed engineer, and the task card then becomes a legal document. Since airlines are increasingly outsourcing their maintenance all over the world, until digital sign-offs are widely accepted in the industry, it doesn't make sense for the airline alone to go fully digital.
It is changing, but due to the highly regulated nature of the industry, innovation can take time to trickle down.

and in many remote places those digital means may not even work reliably...